Okay, bear with me because I don't know how all of this works. If my family's tix are coded onto our room keys do I stick my room key into the machine???
You can UPgrade any WDW ticket at any time while it is valid! You cannot, however, DOWNgrade any ticket.
Check this out, it should answer all your ticket questions:
http://www.allearsnet.com/pl/ticket.htm
The no expiration add on can be added at any point before the ticket expires but you will pay based on how many days the original ticket was for, not how many days are left. Same goes for the Park Hopping and Plus Pack add ons. They may be added at any time within 14 days after first use of the ticket but will be charged at the full rate of the add on regardless of how many unused admissions remain on the ticket. The add ons (PH, Plus and No Expiration) are priced on a *per ticket* cost, not on a per day cost. You may do the add ons at any Guest Relations location in the parks or DTD or at the Guest Services window at any Disney resort.